On Thu, Oct 25, 2012 at 12:49 AM, Markus <li...@neuronenwerk.de> wrote:
> Hi list,
>
> I'm having a device here, that amongst others, features some
> descriptors within the configuration descriptor, that are not
> explicitely available via the libusbx API. These are:
>
> - Interface Association Descriptor
> - Device Class Specific Descriptors
> - Super Speed Companion Descriptor
>
> While I can, for instance, read the IAD via the "extra" field, I
> can't do arbitrary reads - as it looks. If I consider the memory
> contiguous, it will fail. So I'm unable to parse anything that's
> not been wrapped by libusbx, like my Device Class Specific
> Descriptors.
>
> Though the IAD is living directly after the 8 byte configuration
> descriptor head in the config descriptor (within the device),
> the address of "extra" is nearly 7k away from its end.
>
> If the configuration descriptor would be contiguous, it would
> easily be possible to parse the descriptor.
>
> Am I missing something? If not, would you be willing to change
> this, as it would enable a lot more applications with libusbX.
>
We don't use "extra". Not sure what that is for. Sorry!
Here are some copy and pasted sections from our code... Anything that
starts with "u" is our own structs. Sorry if it's a bit cryptic...but
hopefully you get the idea. Just loop through all the descriptors in
the configuration and look for descriptors that have the type
USB_DT_INTERFACE_ASSOCIATION (0x0b).
UINT32 total_length_cfg_desc;
UINT8 *cfg_desc_buffer;
UINT32 config_descriptor_return_length;
UINT8 *cfg_desc_ptr;
UINT8 *interface_assocation_ptr;
BOOL interface_assoc_parsing_done;
UINT32 desc_len;
UINT32 desc_type;
UINT32 next_assoc;
UINT32 rv;
total_length_cfg_desc = ucfg->cfg_desc->wTotalLength;
cfg_desc_buffer = (UINT8 *) malloc( total_length_cfg_desc );
rv = tera_usb_host_stack_configuration_descriptor_get(udev->device_id,
ucfg->cfg_desc->bConfigurationValue,
cfg_desc_buffer,
total_length_cfg_desc,
&config_descriptor_return_length);
cfg_desc_ptr = cfg_desc_buffer;
interface_assoc_parsing_done = FALSE;
ucfg->nr_interface_assocations = 0;
while (!interface_assoc_parsing_done)
{
next_assoc = ucfg->nr_interface_assocations;
if ( next_assoc >= USB_MAX_INTERFACE_ASSOCIATIONS )
{
// ERROR
ucfg->nr_interface_assocations = 0;
return ERROR;
}
desc_len = *cfg_desc_ptr;
desc_type = *(cfg_desc_ptr + 1);
if (desc_type == USB_DT_INTERFACE_ASSOCIATION)
{
// Found an interface association, parse it out
interface_assocation_ptr = cfg_desc_ptr;
uiface_assoc = &ucfg->interface_associations[next_assoc];
uiface_assoc->bLength = *interface_assocation_ptr++;
uiface_assoc->bDescriptorType = *interface_assocation_ptr++;
uiface_assoc->bFirstInterface = *interface_assocation_ptr++;
uiface_assoc->bInterfaceCount = *interface_assocation_ptr++;
uiface_assoc->bFunctionClass = *interface_assocation_ptr++;
uiface_assoc->bFunctionSubClass = *interface_assocation_ptr++;
uiface_assoc->bFunctionProtocol = *interface_assocation_ptr++;
uiface_assoc->iFunction = *interface_assocation_ptr++;
ucfg->nr_interface_assocations++;
}
cfg_desc_ptr += desc_len;
if (cfg_desc_ptr >= total_length_cfg_desc + cfg_desc_buffer)
{
interface_assoc_parsing_done = TRUE;
}
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